[roboeve]

This combines two WhatsApp adapter fixes so they can be reviewed and merged together: #1007 from @armancharan, which sends replies from the number that received the thread, and #909 from @luksch42, which keeps literal text intact when converting Markdown to WhatsApp formatting. Each lands as its own commit with a Co-authored-by trailer, and two follow-up commits build on them. It supersedes #1007 and #909, which can be closed once this merges.

Fixes #988, fixes #908.

A bot connected to more than one WhatsApp number used to reply, react, mark messages read, show typing indicators, and upload media from the configured phoneNumberId, even when the conversation came in on a different number. Outbound calls now use the phone number ID encoded in the thread ID. Because that ID becomes part of the Graph API path, it has to be numeric: a thread ID that doesn't decode, or whose phone number ID contains anything other than digits, throws a ValidationError before any request is made. Each call decodes the thread once and passes it down to the send helpers. The protected helpers still accept the recipient string they took before, and uploadMedia and resolveMedia still default to the configured number, so existing subclasses keep working. openDM and the single-argument markAsRead(messageId) keep using the configured number, since neither has an inbound thread to read from.

On the formatting side, text such as (~80 % easy), C:\Users\Luis, or snake_case_name used to pick up visible Markdown escapes in WhatsApp. WhatsApp has no escape syntax, so the converter now sends text as written and keeps a backslash only where the text would otherwise turn into formatting: a marker that forms a pair on one line, such as \_word\_, a marker touching a formatting marker, and a quote, bullet, or numbered-list marker at the start of a line. This means Literal \*\*stars\*\* now comes out escaped rather than as Literal **stars**, which reverses one assertion from #909. Bold, italic, and strikethrough are rendered from their AST nodes, so markers inside inline and fenced code stay unchanged, intraword italics no longer produce HTML character references like n, and hard breaks are sent as plain newlines.

To support this, stringifyMarkdown in chat gains a handlers option for platform-specific serialization, which is why chat gets a minor changeset:

const md = stringifyMarkdown(ast, {
  handlers: {
    text: (node) => node.value,
  },
});

A few edge cases remain. A marker pair split across formatting, such as ~5 **x** 6~, isn't detected. Intraword *emphasis* like 2*3*4 comes out as 2_3_4. Autolinks are still wrapped in <...>, as they are on main.

pnpm validate passes on the branch. The two carried-over commits from roboeve[bot] don't have a DCO sign-off yet; the follow-up commits do. I haven't sent messages through a live WhatsApp number.

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Project	Deployment	Actions	Updated
chat	Ready	Preview, v0	Oct 19, 2026 2:03am UTC